Noise coherence in closely-spaced electrodes: the implications for spatial averaged ECG recordings

Ensemble signal averaging is conventionally used to reduce the noise content of ECG recordings. One shortcoming of this technique is that it removes the possibility of registering transient signals. As a consequence the simultaneous averaging of spatially related leads has been used. This relies on the recording electrodes receiving correlated signal components for reinforcement together with uncorrelated noise. We have developed a methodology for studying EMG noise reduction by spatial averaging and present results for different electrode spacings which suggest minimum separations for noise rejection.